The present disclosure is directed toward a supercharged engine that uses electronic throttle control.
A supercharger (also known as a blower, a positive displacement pump, or a centrifugal pumper) can be used to increase the effective displacement of an engine by forcing a relatively high volume of air into the cylinders for combustion. The additional mass of oxygen that is forced into the cylinders allows the engine to bum more fuel, which improves the volumetric efficiency of the engine and makes it more powerful. A supercharger can be mechanically powered from the engine's crankshaft or from another power source, such as an electric battery.
Electronic throttle control (ETC) can be used to control air throttle without directly mechanically linking the accelerator pedal to the air throttle. This can be accomplished by using a throttle position sensor to feed throttle-position data to a computer. The computer can process the data to decide a desired throttle position, which can be controlled with a solenoid or similar mechanism.
The inventors herein have recognized that several challenges exist in designing an engine that uses a supercharger and ETC. In a pedal-follower based ETC system, in which throttle angle can be monitored, a supercharger affects air-fuel control. Furthermore, the addition of torque based control of throttle position substantially increases the challenges of accurately monitoring and delivering airflow. Potential supercharger DEGRADATION including over-boosting or under-boosting further increase the challenges of operating a supercharger in a drive system that includes electronic throttle control.
At least some of the issues associated with a supercharged ETC engine may be addressed by a drive system including an engine configured to convert chemical energy into mechanical energy, an electronically-controlled air throttle configured to regulate air delivery to the engine, a supercharger configured to selectively increase pressure of the air delivered to the engine, and a supercharger diagnostic system configured to diagnose supercharger over-boosting or under-boosting.